1. Field of the Invention
This invention relates to a speed-change gear to be mounted outside a bicycle having a multi-step sprocket assembly, which speed-change gear shifts a bicycle-driving chain among different steps of the sprocket assembly.
2. Description of the Prior Art
The inventors have disclosed a speed-change gear to be mounted outside a bicycle in Japanese Patent Application No. 90,492/75, which was laid open as Japanese Patent Laying-open Specification No. 15,033/77. The disclosed speed-change gear has shortcomings in that, in addition to shafts holding a parallel link means, a separate shaft is secured to a fitting member so as to rotatably hold a speed-change actuating cam, a reel connected to an operating wire means, and a spring, so that the speed-change gear is complicated in construction and comparatively heavy, and that the disclosed speed-change gear has an adjusting bolt and the like projecting to the outside of the bicycle so that the projecting bolt and the like may come in contact with a person and hurt him.